5:15 PM - 6:45 PM
[ACG42-P05] The influence of Arctic runoff on the Atlantic meridional overturning circulation
Keywords:Atlantic Meridional Overturning Circulation, Deep Convection, Runoff, Ocean general circulation model
The Atlantic meridional Overturning Circulation (AMOC) has a significant impact on climate in terms of heat transport. AMOC starts with deep-water formation in the high latitudes of the North Atlantic. The deep-water formation is driven by deep convection caused by the densification of surface water due to sea surface cooling, and the inflow of seawater from the Arctic, which has a lower salinity than the deep convection site, weakens deep convection. Runoff is the largest source of freshwater in the Arctic Ocean, and its amount is projected to increase with global warming. Thus, it is important to assess the impact of Arctic runoff on the AMOC. However, the extent of the impact of rivers on the AMOC and the specific mechanisms involved have not yet been elucidated.
In this study, using the ocean general circulation model COCO, experiments were conducted in which the same amount of flow was reduced from Arctic rivers to assess the impact of Arctic runoff on the AMOC quantitatively. The results showed that the impact on the AMOC was stronger for runoff on the Russian side of the Arctic than for runoff on the North American side of the Arctic. This was found to be due to the greater contribution of Russian rivers' runoff to freshwater transport to the Labrador Sea, the largest deep convection site in the AMOC, compared to rivers' on the North American side.
It was also shown that the timescale of the response of deep convection and AMOC to changes in Arctic runoff is around 80 years, which can be explained by the timescale of density flux convergence in the Labrador Sea. The time scale of this density flux convergence was shown to be explained by the superposition of changes in salt transport from the Arctic due to the reduction of runoff, changes in salinity, temperature, and circulation in the south-eastern part of the Labrador Sea, and changes in heat and freshwater fluxes at the sea surface.
In this study, using the ocean general circulation model COCO, experiments were conducted in which the same amount of flow was reduced from Arctic rivers to assess the impact of Arctic runoff on the AMOC quantitatively. The results showed that the impact on the AMOC was stronger for runoff on the Russian side of the Arctic than for runoff on the North American side of the Arctic. This was found to be due to the greater contribution of Russian rivers' runoff to freshwater transport to the Labrador Sea, the largest deep convection site in the AMOC, compared to rivers' on the North American side.
It was also shown that the timescale of the response of deep convection and AMOC to changes in Arctic runoff is around 80 years, which can be explained by the timescale of density flux convergence in the Labrador Sea. The time scale of this density flux convergence was shown to be explained by the superposition of changes in salt transport from the Arctic due to the reduction of runoff, changes in salinity, temperature, and circulation in the south-eastern part of the Labrador Sea, and changes in heat and freshwater fluxes at the sea surface.